Individuals with Parkinson’s disease are at a higher risk of developing nutrient deficiencies for several interconnected reasons. Understanding these factors is crucial because insufficient nutrients can worsen symptoms, reduce medication effectiveness, and compromise energy, exercise capacity, and overall health (4).

1. Altered Gut Microbiome

Research shows that people with Parkinson’s often have an imbalanced gut microbiota, which affects the digestion and absorption of essential nutrients. The gut microbiome plays a central role in breaking down food, producing certain vitamins, and regulating inflammation. A disrupted microbiome can lead to:

• Reduced absorption of vitamins such as B12, folate, and biotin.
• Impaired conversion of nutrients into their active forms.
• Increased gastrointestinal inflammation, which can worsen constipation and bloating.
• Altered metabolism of medications, reducing their effectiveness (5).

2. Age-Related Declines in Digestive Enzymes and Stomach Acid

As we age, the production of stomach acid and digestive enzymes naturally declines, making it more difficult to digest and absorb nutrients from food. This is compounded in Parkinson’s, as many patients experience gastroparesis (delayed stomach emptying) or slower intestinal motility. The consequences include:

• Poor protein absorption, leading to reduced amino acids for dopamine synthesis.
• Decreased absorption of vitamins such as B12 and minerals like iron and magnesium.
• Increased fatigue and weakness due to chronic undernutrition (6).

3. Constipation and Slow Gastrointestinal Transit

Constipation is a common non-motor symptom of Parkinson’s disease and can significantly impact nutrient absorption. Slower gut transit time means:

• Nutrients may not be fully absorbed before food passes through the intestines.
• Medications, especially levodopa, may have delayed or reduced absorption.
• Gastrointestinal discomfort may reduce appetite, leading to lower overall nutrient intake (7).

4. Dietary Limitations and Appetite Changes

People with Parkinson’s may also experience loss of appetite due to taste changes, depression, or medication side effects. Difficulty chewing or swallowing, leading to avoidance of protein-rich or fibrous foods. Reduced energy intake, which can further exacerbate nutrient deficiencies

All these factors mean that even individuals who try to eat a balanced diet may not get enough nutrients from food alone, highlighting the need for personalised nutrition strategies (6).

5. Parkinson’s Medications Interact with Food

Levodopa, often combined with carbidopa or benserazide, is the most commonly prescribed medication for Parkinson’s disease because it temporarily replenishes dopamine levels (8). However, levodopa competes with amino acids from dietary protein for absorption in the small intestine and transport into the brain. This means that consuming high-protein meals too early in the day can reduce the medication’s effectiveness, potentially worsening symptoms such as tremors, stiffness, and slowness of movement. To address this, many neurologists and nutritionists recommend eating most protein later in the day—after the most active morning and early afternoon doses—a strategy known as a “protein redistribution diet.” This approach helps the medication work more effectively while still ensuring adequate daily protein intake (9).

In addition to levodopa, people with Parkinson’s may also take other medications, including dopamine agonists (pramipexole, ropinirole), MAO-B inhibitors (selegiline, rasagiline), and COMT inhibitors (entacapone) (10). Long-term use of some Parkinson’s medications can deplete important vitamins and minerals, such as B vitamins (B6, B12, folate) (11) and other nutrients depending on the medication. Deficiencies in these nutrients can worsen fatigue, cognitive function, mood, and overall neurological health.

6. Brain Inflammation and Neuronal Damage

In addition to nutrient depletion and dopamine loss, chronic inflammation in the brain is a key factor in Parkinson’s progression. Dying neurons trigger microglial cells in the brain, which release inflammatory molecules like cytokines and free radicals, further damaging dopamine-producing neurons. This creates a vicious cycle of neuron death, worsening motor and non-motor symptoms (12). Targeted nutrients such as magnesium threonate, omega-3 fatty acids, vitamin D, polyphenols, CoQ10, and B-group vitamins play a crucial role in reducing brain inflammation, supporting neuronal function, and combating oxidative stress (13). As we age—and particularly in Parkinson’s—our bodies absorb these nutrients less efficiently, making supplementation an important strategy to help protect brain health and slow disease progression.